Tracking a reference picture on an electronic device

ABSTRACT

Methods for decoding a video bitstream. One of the methods includes receiving a respective buffer description for each of one or more decoded reference pictures from the video bitstream; wherein the respective buffer descriptions include a poc cycle parameter for one or more long term reference pictures in the one or more decoded reference pictures, and wherein the poc cycle parameter is used to calculate a picture order count (POC) for the decoded long term reference pictures; identifying one or more decoded reference pictures for a current picture from a decoded picture buffer, based on the POC for the decoded long term reference pictures; decoding the current picture using inter-frame prediction based on the identified one or more decoded reference pictures; and buffering the decoded picture in the decoded picture buffer.

RELATED REFERENCES

This application is a continuation of U.S. patent application Ser. No.13/273,191, entitled “TRACKING A REFERENCE PICTURE ON AN ELECTRONICDEVICE,” filed on Oct. 13, 2011, which is hereby incorporated byreference herein, in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to electronic devices. Morespecifically, the present disclosure relates to enabling tracking of areference picture.

BACKGROUND

Electronic devices have become smaller and more powerful in order tomeet consumer needs and to improve portability and convenience.Consumers have become dependent upon electronic devices and have come toexpect increased functionality. Some examples of electronic devicesinclude desktop computers, laptop computers, cellular phones, smartphones, media players, integrated circuits, etc.

Some electronic devices are used for processing and displaying digitalmedia. For example, portable electronic devices now allow for digitalmedia to be consumed at almost any location where a consumer may be.Furthermore, some electronic devices may provide download or streamingof digital media content for the use and enjoyment of a consumer.

The increasing popularity of digital media has presented severalproblems. For example, efficiently representing high-quality digitalmedia for storage, transmittal and playback presents several challenges.As can be observed from this discussion, systems and methods thatrepresent digital media more efficiently may be beneficial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example of one or moreelectronic devices in which systems and methods for tracking a referencepicture may be implemented;

FIG. 2 is a block diagram illustrating one configuration of a decoder;

FIG. 3 is a flow diagram illustrating one configuration of a method fortracking a reference picture with reduced overhead referencing;

FIG. 4 is a flow diagram illustrating a more specific configuration of amethod for tracking a reference picture with reduced overheadreferencing;

FIG. 5 is a diagram illustrating one example of multiple picture setsreferenced by cycle parameters;

FIG. 6 is a diagram illustrating one example of signaling a wrapindicator in accordance with the systems and methods disclosed herein;

FIG. 7 is a flow diagram illustrating another more specificconfiguration of a method for tracking a reference picture with reducedoverhead referencing;

FIG. 8 is a flow diagram illustrating one configuration of a method 800for determining whether a transition has occurred between picture sets;

FIG. 9 is a flow diagram illustrating another more specificconfiguration of a method for tracking a reference picture with reducedoverhead referencing; and

FIG. 10 illustrates various components that may be utilized in anelectronic device.

DETAILED DESCRIPTION

A method for tracking a reference picture on an electronic device isdescribed. The method includes receiving a bitstream. The method alsoincludes decoding a portion of the bitstream to produce a decodedreference picture. The method further includes tracking the decodedreference picture in a decoded picture buffer (DPB) with reducedoverhead referencing. The method additionally includes decoding apicture based on the decoded reference picture. A cycle parameter may berepresented by a signed integer or an unsigned integer. Decoding thepicture may be based on one or more decoded reference pictures.

Tracking the decoded reference picture may include associating a cycleparameter with a decoded picture set that includes the decoded referencepicture. Tracking the decoded reference picture may also includedetermining whether a wrap indicator is received. Tracking the decodedreference picture may further include modifying the cycle parameter if awrap indicator is received.

Tracking the decoded reference picture may include associating a cycleparameter with a decoded picture set that includes the decoded referencepicture. Tracking the decoded reference picture may also includedetermining whether a transition has occurred between picture sets.Tracking the decoded reference picture may further include modifying thecycle parameter if the transition has occurred.

Determining whether a transition has occurred between picture sets mayinclude determining whether a first picture order count (POC) of acurrent picture being decoded is less than a second POC of a lastdecoded picture and whether the second POC minus the first POC isgreater than a first threshold. Determining whether a transition hasoccurred may also include determining that a transition from an earlierpicture set has occurred if the first POC is less than the second POCand if the second POC minus the first POC is greater than the firstthreshold. Determining whether a transition has occurred mayadditionally include determining whether the first POC is greater thanthe second POC and whether the first POC minus the second POC is greaterthan a second threshold. Determining whether a transition has occurredmay also include determining that a transition from a later picture sethas occurred if the first POC is greater than the second POC and if thefirst POC minus the second POC is greater than the second threshold.Determining whether a transition has occurred may further includedetermining that no transition has occurred otherwise.

A buffer description of the decoded reference picture may include apicture order count (POC), a cycle parameter and a temporal identifier.A buffer description of the decoded reference picture may include a slotindex that points to a location in the DPB. A buffer description of thedecoded reference picture may include a function of a picture ordercount (POC) and a cycle parameter as well as a temporal identifier.

An adaptive slice parameter set or adaptation parameter set (APS) mayinclude a number of reference pictures, a picture order count, a pictureorder count cycle parameter, a temporal identifier picture order countparameter, a picture parameter set number of reference pictures, apicture parameter set picture order count, a picture parameter setpicture order count cycle parameter and/or a picture parameter settemporal identifier picture order count parameter. A received sliceheader may include a number of reference pictures, a picture ordercount, a picture order count cycle parameter, a temporal identifierpicture order count parameter, a picture parameter set number ofreference pictures, a picture parameter set picture order count, apicture parameter set picture order count cycle parameter and/or apicture parameter set temporal identifier picture order count parameterseparately from buffer description information.

Tracking the decoded reference picture may be based on an informationsubindex and a picture order count parameter or a picture parameter set(PPS) picture order count parameter. A subset of received pictures maybe referenced using delta referencing and a subset of received picturesmay be referenced using absolute referencing.

An electronic device configured for tracking a reference picture is alsodescribed. The electronic device includes a processor and instructionsstored in memory that is in electronic communication with the processor.The electronic device receives a bitstream. The electronic device alsodecodes a portion of the bitstream to produce a decoded referencepicture. The electronic device further tracks the decoded referencepicture in a decoded picture buffer (DPB) with reduced overheadreferencing. The electronic device additionally decodes a picture basedon the decoded reference picture.

The systems and methods disclosed herein describe several configurationsfor tracking a reference picture on an electronic device. For example,the systems and methods disclosed herein describe tracking a decodedreference picture in a decoded picture buffer (DPB) with reducedoverhead referencing. For instance, several approaches for long termreference picture signaling are described. It should be noted that thedecoded picture buffer (DPB) may be a buffer holding decoded picturesfor reference, output reordering, or output delay specified for ahypothetical reference decoder.

On an electronic device, a decoded picture buffer (DPB) may be used tostore reconstructed (e.g., decoded) pictures at a decoder. These storedpictures may then be used, for example, in an inter-predictionmechanism. When pictures are decoded out of order, the pictures may bestored in the DPB so they can be displayed later in order.

In the H.264 or advance video coding (AVC) standard, DPB management(e.g., deletion, addition of pictures, reordering of pictures, etc.) iscarried out using memory management control operations (MMCO). For theupcoming high efficiency video coding (HEVC) standard, more reliable DPBmanagement approaches are under consideration. One example of a morereliable approach is based on absolute signaling of reference picturesas detailed in “Absolute signaling of reference pictures” from the JointCollaborative Team on Video Coding (JCT-VC) document JCTVC-F493.

JCTVC-F493 outlines absolute signaling of reference pictures to identifywhich reference pictures should be kept in the decoded picture buffer(DPB). In particular, it outlines two different approaches to identifywhich reference pictures are to be kept in the DPB based on a pictureorder count (POC). The picture order count (POC) may be a variable thatis associated with each encoded picture and has a value that isincreasing with increasing picture position in an output order withwrap-around.

In one example, assume that all pictures have a temporal identifier(temporalID)=0. Further assume that the current POC=5 and that thecurrent DPB contains={3, 2}. Additionally assume that a definition inthe Picture Parameter Set (PPS) is: BufferDescription0={deltaPOC=−1,temporalID=0}, {deltaPOC=−2, temporalID=0}. One approach given is toreference a buffer description in the PPS. In this approach, the sliceheader of a picture with POC=5 contains a reference toBufferDescription0 in the PPS. Assume that an action is to drop adecoded picture with POC=2 from the DPB and to add a decoded picturewith POC=4 to the DPB. As a result, the DPB then contains={4, 3}.

It should be noted that a temporalID may be defined as follows in theJoint Collaborative Team on Video Coding (JCT-VC) document JCTVC-F803:“temporalID specifies a temporal identifier for the NAL unit. The valueof temporalID shall be the same for all NAL units of an access unit.When an access unit contains any NAL unit with the nal_unit_type equalto 5, temporalID shall be equal to 0.” It should be noted that NAL maybe an abbreviation for “network abstraction layer.”

Another approach is to explicitly signal the contents of the DPB using adelta POC with respect to the current POC. In this approach, the sliceheader of a picture with POC=5 contains {deltaPOC=−1, temporalID=0} and{deltaPOC=−2, temporalID=0}. Assume that an action is to drop a decodedpicture with POC=2 from the DPB and to add a decoded picture POC=4 tothe DPB. As a result, the new DPB contains={4, 3}.

Some advantages of the approaches given by JCTVC-F493 are as follows.The approaches in JCTVC-F493 provide a simple mechanism. Furthermore, aloss of a picture is easily detected at the decoder. Additionally,dropping of entire layers of pictures with a higher temporal ID may bedetected and well supported.

However, some disadvantages of the approaches given in JCTVC-F493 aregiven hereafter. The bit overhead for signaling a long-term referencepicture can become large. Furthermore, a fixed number of bits may beallocated to communicate a POC. As a result, when a maximum valueallowed by the number of bits being used is reached, the POC numberingshould wrap around to 0. Thus, it may not be possible to guarantee thatpictures can be uniquely identified using the POC.

The systems and methods disclosed herein may help to mitigate thesedisadvantages. In particular, the systems and methods disclosed hereinmay be beneficial by reducing the overhead associated with absolute longterm picture referencing and may enable pictures to be uniquelyidentified (e.g., a long-term (reference) picture may not be confusedwith other short-term or long-term pictures and vice-versa).

The systems and methods disclosed herein may provide one or moreadditional benefits that are described as follows. One or moreconfigurations of the systems and methods disclosed herein may make fulluse of the available POC numbering space [0, . . . , MaxPOC−1], whereMaxPOC=2^(log2) ^(_) ^(max) ^(_) ^(pic) ^(_) ^(order) ^(_) ^(cnt) ^(_)^(minus4+4) and log2_max_pic_order_cnt_minus4 specifies the value of thevariable MaxPOC that is used in the decoding process for picture ordercount. For example, one prior approach to resolving re-use of [0, . . ., MaxPOC−1] after a POC wrap-around advocates that the POC currently inuse are stepped over when assigning an identifier (e.g., a POC number)to a picture. This results in part of the POC space not being used.However, the systems and methods disclosed herein may resolve thestepping over of POC and the associated POC space shrinkage issue.

Another benefit may be that some configurations of the systems andmethods disclosed herein for signaling may be self-contained in eachpicture. Thus, error resilience may be better compared to a scheme thatrelies on information propagation from previous pictures (that could getlost or dropped). For example, one configuration of the decoded picturebuffer (DPB) description does not rely on information embedded in otherpictures to maintain the same DPB as an encoder.

Yet another benefit of some configurations of the systems and methodsdisclosed herein may be that if a picture is lost, the loss can bedetected as soon as a buffer description is available at the decoder(which is at the next received picture). This allows the decoder to takecorrective action. Yet another benefit is that if the POC resolution issufficient, no extra bits are required.

Various configurations are now described with reference to the Figures,where like reference numbers may indicate functionally similar elements.The systems and methods as generally described and illustrated in theFigures herein could be arranged and designed in a wide variety ofdifferent configurations. Thus, the following more detailed descriptionof several configurations, as represented in the Figures, is notintended to limit scope, as claimed, but is merely representative of thesystems and methods.

FIG. 1 is a block diagram illustrating an example of one or moreelectronic devices 104 in which systems and methods for tracking areference picture may be implemented. In this example, electronic deviceA 104 a and electronic device B 104 b are illustrated. However, itshould be noted that the features and/or functionality described inrelation to electronic device A 104 a and electronic device B 104 may becombined into a single electronic device in some configurations.

Electronic device A 104 a includes an encoder 108 and an overheadsignaling module 112. Each of the elements included within electronicdevice A 104 a (e.g., the encoder 108 and the overhead signaling module112) may be implemented in hardware, software or a combination of both.

Electronic device A 104 a may obtain an input picture 106. In someconfigurations, the input picture 106 may be captured on electronicdevice A 104 a using an image sensor, retrieved from memory and/orreceived from another electronic device.

The encoder 108 may encode the input picture 106 to produce encoded data110. For example, the encoder 108 may encode a series of input pictures106 (e.g., video). In one configuration, the encoder 108 may be ahigh-efficiency video coding (HEVC) encoder. The encoded data 110 may bedigital data (e.g., a bitstream).

The overhead signaling module 112 may generate overhead signaling basedon the encoded data 110. For example, the overhead signaling module 112may add overhead data to the encoded data 110 such as slice headerinformation, picture parameter set (PPS) information, picture ordercount (POC), reference picture designation, etc. In some configurations,the overhead signaling module 112 may produce a wrap indicator thatindicates a transition between two sets of pictures.

More detail on kinds of overhead signaling that may be produced byelectronic device A 104 a is given below. In particular, none, one ormore of the parameters, indicators or kinds of information described inrelation to decoding below may be produced by the overhead signalingmodule 112, depending on the configuration. It should be noted that theoverhead signaling module 112 may be included within the encoder 108 insome configurations. The overhead signaling module 112 may enablepicture tracking with reduced overhead referencing.

The encoder 108 (and overhead signaling module 112, for example) mayproduce a bitstream 114. The bitstream 114 may include encoded picturedata based on the input picture 106. In some configurations, thebitstream 114 may also include overhead data, such as slice headerinformation, PPS information, etc. More detail on overhead data is givenbelow. As additional input pictures 106 are encoded, the bitstream 114may include one or more encoded pictures. For instance, the bitstream114 may include one or more encoded reference pictures and/or otherpictures.

The bitstream 114 may be provided to a decoder 102. In one example, thebitstream 114 may be transmitted to electronic device B 104 b using awired or wireless link. In some cases, this may be done over a network,such as the Internet or a Local Area Network (LAN). As illustrated inFIG. 1, the decoder 102 may be implemented on electronic device B 104 bseparately from the encoder 108 on electronic device A 104 a. However,it should be noted that the encoder 108 and decoder 102 may beimplemented on the same electronic device in some configurations. In animplementation where the encoder 108 and decoder 102 are implemented onthe same electronic device, for instance, the bitstream 114 may beprovided over a bus to the decoder 102 or stored in memory for retrievalby the decoder 102.

The decoder 102 may be implemented in hardware, software or acombination of both. In one configuration, the decoder 102 may be ahigh-efficiency video coding (HEVC) decoder. The decoder 102 may receive(e.g., obtain) the bitstream 114. The decoder 102 may generate a decodedpicture 118 (e.g., one or more decoded pictures 118) based on thebitstream 114. The decoded picture 118 may be displayed, played back,stored in memory and/or transmitted to another device, etc.

The decoder 102 may include a reference picture tracking module 116. Thereference picture tracking module 116 may enable the decoder 102 totrack a reference picture with reduced overhead referencing. Forexample, the reference picture tracking module 116 may track a referencepicture in a decoded picture buffer (DPB) using less overhead than isneeded with prior approaches, such as approaches given in JCTVC-F493.

In prior approaches, for example, non-reduced overhead referencing maybe used to specify the relationship between a current picture and a longterm reference picture. In prior approaches, for instance, therelationship between a current picture and a long term reference picturemay be specified by increasing the POC numbering space and therebyavoiding the POC wraparound issue. However, increasing the POC numberingspace can only be achieved at the expense of an increasedbit-requirement for POC. This example is one of several possiblemechanisms that can be used to avoid the POC wrap around issue in priorapproaches. However, this particular example demonstrates the largeroverhead aspect for long-term pictures in prior approaches.

JCTVC-F493, for example, used a longterm_poc[i] field in a bufferdescription that specified an absolute POC and a longterm_temporal_id[i]field in the buffer description that specified a temporal ID for a longterm picture. This was later removed in JCTVC-F803, which did notinclude a mechanism for long term pictures. In subsequent discussions,an approach of stepping over (long term picture) POCs was given.

Problems may arise with the prior approaches. First, a large amount ofoverhead data may be needed to specify the relationship between a longterm reference picture and another picture. For instance, a large numberof overhead bits may need to be allocated to adequately represent aninteger number difference in POC between the long term reference pictureand another picture. Second, if a limited number of bits is specified torepresent this difference, the difference may be ambiguously indicatedwhen numbers are reused (because of number set cycling, for example).

The reference picture tracking module 116 may use one or more approachesor methods that are described in greater detail below in order to reducereferencing overhead. Some examples include using a cycle parameter anddecrementing the cycle parameter based on wrap indicators or transitionsbetween sets of pictures.

FIG. 2 is a block diagram illustrating one configuration of a decoder202. The decoder 202 may be included in an electronic device 204. Forexample, the decoder 202 may be a high-efficiency video coding (HEVC)decoder. The decoder 202 and/or one or more of the elements illustratedas included in the decoder 202 may be implemented in hardware, softwareor a combination of both. The decoder 202 may receive a bitstream 214(e.g., one or more encoded pictures included in the bitstream 214) fordecoding. In some configurations, the received bitstream 214 may includereceived overhead information, such as a received slice header, receivedPPS, received buffer description information, etc. The encoded picturesincluded in the bitstream 214 may include one or more encoded referencepictures and/or one or more other encoded pictures.

Received symbols (in the one or more encoded pictures included in thebitstream 214) may be entropy decoded by an entropy decoding module 254,thereby producing a motion information signal 256 and quantized, scaledand/or transformed coefficients 258.

The motion information signal 256 may be combined with a portion of areference frame signal 284 from a frame memory 264 at a motioncompensation module 260, which may produce an inter-frame predictionsignal 268. The quantized, descaled and/or transformed coefficients 258may be inverse quantized, scaled and inverse transformed by an inversemodule 262, thereby producing a decoded residual signal 270. The decodedresidual signal 270 may be added to a prediction signal 278 to produce acombined signal 272. The prediction signal 278 may be a signal selectedfrom either the inter-frame prediction signal 268 or an intra-frameprediction signal 276 produced by an intra-frame prediction module 274.In some configurations, this signal selection may be based on (e.g.,controlled by) the bitstream 214.

The intra-frame prediction signal 276 may be predicted from previouslydecoded information from the combined signal 272 (in the current frame,for example). The combined signal 272 may also be filtered by ade-blocking filter 280. The resulting filtered signal 282 may be writtento frame memory 264. The resulting filtered signal 282 may include adecoded picture.

The frame memory 264 may include a decoded picture buffer (DPB) asdescribed herein. The DPB may include one or more decoded pictures thatmay be maintained as short or long term reference frames. The framememory 264 may also include overhead information corresponding to thedecoded pictures. For example, the frame memory 264 may include sliceheaders, picture parameter set (PPS) information, cycle parameters,buffer description information, etc. One or more of these pieces ofinformation may be signaled from an encoder (e.g., encoder 108, overheadsignaling module 112).

The decoder 202 may include a reference picture tracking module 216. Thereference picture tracking module 216 may track one or more referencepictures in the frame memory 264 with reduced referencing overhead. Inone example, the reference picture tracking module 216 may track longterm reference pictures using a cycle parameter and modifying (e.g.,decrementing) the cycle parameter based on received wrap indicators. Inanother example, an update of all reference picture cycle parameters maybe carried out with respect to the picture being decoded. This updateprocedure may be executed once for the current picture (e.g., thepicture being decoded). The transition between cycles may be kept trackof implicitly with the help of the POC. At times the cycle parameter maybe increased (when the transition is from picture set ‘n’ to picture set‘n−1’ as may occur in out-of-order picture decoding, for example).Greater detail on one or more approaches to tracking a reference pictureis given below.

Some configurations of the systems and methods disclosed herein may usea modified buffer description. Examples of the modified bufferdescription are given hereafter. The buffer description may be modifiedto include “POC,” “poc_cycle” and “temporalID” for long-term referencepictures. It should be noted that “poc_cycle” may be one example of thecycle parameter described herein. The (modified) buffer descriptions,(modified) syntaxes and/or parameters given in accordance with thesystems and methods disclosed herein may enable reduced overheadreferencing.

Table (1) below gives one example comparing the buffer descriptionwithin the PPS in a prior approach and one proposed approach inaccordance with the systems and methods disclosed herein. The priorapproach is detailed in the “candidate working draft text of ad-hocgroup 21” document (AHG21) that was created to further the work inJCTVC-F493. It should be noted that AHG21 (JCTVC-F803) separately groupsand specifies “negative pictures” (e.g., those that have negativedeltaPOC values) and “positive pictures” (e.g., those pictures that havepositive deltaPOC values).

TABLE (1) AHG21 Buffer Description Proposed Buffer DescriptiondeltaPOC₀, temporalID₀ deltaPOC₀, temporalID₀ deltaPOC₁, temporalID₁deltaPOC₁, temporalID₁ deltaPOC₂, temporalID₂ deltaPOC₂, temporalID₂deltaPOC₃, temporalID₃ (POC₀, poc_cycles₀, temporalID₃) deltaPOC₄,temporalID₄ (POC₁, poc_cycles₁, temporalID₄)In Table (1) illustrated above, (POC_(O3) poc_cycles₀, temporalID₃) and(POC₁, poc_cycles₁, temporalID₄) represent long-term (reference)pictures. It should be noted that the buffer description may contain twolists POCBD and TemporalIDBD for short-term reference pictures(corresponding to POC and TemporalID fields, respectively). Furthermore,the buffer description may contain three lists: POCBD, POC_CYCLE_BD andTemporalIDBD for long-term reference pictures (corresponding to POC,poc_cycle and TemporalID fields, respectively).

It should be noted that the syntax given in AHG21 does not adequatelysupport fixed long term referencing. Listing (1) below illustrates oneexample of a bitstream syntax modification required to a candidateworking draft text of ad-hoc group 21 (AHG21). The changes due to theprior approach are given in bold text in Listing (1).

Listing (1) /* Picture parameter set RBSP syntax  ue(v): Unsignedinteger, entropy coded variable length  se(v): Signed integer, entropycoded variable length  u(x): Unsigned x-bit(s) integer */pic_parameter_set_rbsp( ) {  ... bits_for_temporal_id_in_buffer_descriptions //u(2) positive_pictures_in_buffer_descriptions_flag //u(1) number_of_bds //ue(v)  if( number_of_bds > 0 ) { for(i = 0; i <number_of_bds; i++){  number_of_negative_pictures_pps[i] //ue(v)  for( j= 0; j < number_of_negative_pictures_pps[i]; j++ ) { ...  }  if(positive_pictures_in_buffer_descriptions_flag ){number_of_positive_pictures_pps[i] //ue(v) for( j = 0; j <number_of_positive_pictures_pps[i]; j++ ) { delta_poc_minus_one_pps[i][j] //ue(v)  if(bits_for_temporal_id_in_buffer_descriptions > 0 )temporal_id_positive_pps[i][j] //u(v) }  } number_of_longterm_pictures_pps[i] //ue(v)  for( j = 0; j <number_of_longterm_pictures_pps[i]; j++ ) { poc_pps[i][j] //ue(v)poc_cycle_pps[i][j] //ue(v) or se(v) may be used if(bits_for_temporal_id_in_buffer_descriptions > 0 ) temporal_id_poc_pps[i][j] //u(v)  } }  }  ... }

Examples or descriptions or the parameters in Listing (1) are given asfollows. number_of_longterm_pictures_pps[i] specifies the number ofentries in the list POCBD[i] and POC_CYCLE_BD[i]. The value ofnumber_of_longterm_pictures_pps[i] shall be in the range of 0 tomax_num_ref_frames, inclusive. max_num_ref_frames specifies the maximumnumber of short term and long term reference frames. poc_pps[i][j]specifies POC value and defines the value of the variable POCBD[i][j] asPOCBD[i][j]=poc_pps[i][j]. poc_pps[i][j] shall be in the range of 0 toMaxPOC-1.

poc_cycle_pps[i][j] specifies poc_cycle (e.g., the cycle parameter)value and defines the value of the variable POC_CYCLE_BD as:POC_CYCLE_BD[i][j]=poc_cycle_pps[i][j]. poc_cycle_pps[i][j] (e.g., thecycle parameter) may be less than or equal to zero in someconfigurations. In such a case, a signed integer may be used torepresent the cycle parameter. In other configurations, an unsignedinteger may be used to represent the cycle parameter.

temporal_id_poc_pps[i][j] specifies a temporal identifier and shall bepresent if bits_for_temporal_id_in_buffer_descriptions>0.temporal_id_poc_pps[i][j] defines the value of the variableTemporalIDBD_pps[i][j] asTemporalIDBD_pps[i][j]=temporal_id_poc_pps[i][j].temporal_id_poc_pps[i][j] shall be in the range of 0 tomax_temporal_layers_minus1, inclusive. max_temporal_layers_minus1+1specifies the maximum number of temporal layers present in a sequence.

Listing (2) below illustrates an alternative example configuration wheremultiple buffer descriptions may be created within a PPS with differentcycle parameters (e.g., poc_cycles) using the following syntax. Thechanges due to the prior approach are given in bold text in Listing (2).

Listing (2) /* Picture parameter set RBSP syntax  ue(v): Unsignedinteger, entropy coded variable length  se(v): Signed integer, entropycoded variable length  u(x): Unsigned x-bit(s) integer */pic_parameter_set_rbsp( ) {  ... bits_for_temporal_id_in_buffer_descriptions //u(2) positive_pictures_in_buffer_descriptions_flag //u(1) number_of_bds //ue(v)  if( number_of_bds > 0 ) { for(i = 0; i <number_of_bds; i++){  number_of_negative_pictures_pps[i] //ue(v)  for( j= 0; j < number_of_negative_pictures_pps[i]; j++ ) { ...  }  if(positive_pictures_in_buffer_descriptions_flag ){number_of_positive_pictures_pps[i] //ue(v) for( j = 0; j <number_of_positive_pictures_pps[i]; j++ ) { delta_poc_minus_one_pps[i][j] //ue(v)  if(bits_for_temporal_id_in_buffer_descriptions > 0 )temporal_id_positive_pps[i][j] //u(v) }  } number_of_longterm_pictures_pps[i] //ue(v)  for( j = 0; j <number_of_longterm_pictures_pps[i]; j++ ) { poc_pps[i][j] //ue(v)poc_cycle_pps[i][j] //ue(v) or se(v) may be usedpoc_cycle_steps_flag//u(1) if (poc_cycle_steps_flag) { poc_cycle_steps //ue(v) } if(bits_for_temporal_id_in_buffer_descriptions > 0 ) temporal_id_poc_pps[i][j] //u(v)  } }  }  ... }

In Listing (2), examples of descriptions of further parameters are givenas follows. When set to 1, poc_cycle_steps_flag specifies thatadditional buffer descriptions shall be generated for the signaledbuffer description model that are identical to the signaled bufferdescription model except for the poc_cycle count. poc_cycle_steps_flagshall be 0 by default. Furthermore, poc_cycle_steps specifies the numberof additional buffer descriptions that shall be generated for thesignaled buffer description model. The additional buffer descriptionsshall be identical to the signaled buffer description except that thepoc_cycle count shall be decreased. In one configuration, the additionalbuffer descriptions generated have poc_cycle_pps[i][j] values of −1, −2,−3, . . . , −(poc_cycle_steps).

Listing (3) illustrates another example of syntax modification for thePPS from AHG21. In particular, Listing (3) illustrates one example ofbuffer description syntax used in slice headers as outlined in AHG21.However, modifications to the syntax given in AHG21 in accordance withthe systems and methods disclosed herein are denoted in bold text inListing (3).

Listing (3) /* ue(v): Unsigned integer, entropy coded variable length se(v): Signed integer, entropy coded variable length  u(x): Unsignedx-bit(s) integer */ buffer_description( ) {  bd_reference_flag //u(1) if(bd_reference_flag = = 1) { bd_idx //u(v) bd_poc_cycle_update_flag//u(1) if (bd_poc_cycle_update_flag == 1)  for( j = 0; j <number_of_longterm_pictures_pps[bd_idx]; j++ ) {poc_cycle_pps_override[bd_idx][j]//may be ue(v) or se(v)  }  } else {number_of_negative_pictures //ue(v) for( i = 0; i <number_of_negative_pictures; i++ ) { ... } if(positive_pictures_in_buffer_descriptions_flag ){ ... }number_of_longterm_pictures //ue(v) for( j = 0; j <number_of_longterm_pictures; j++ ) {  poc[i][j] //ue(v)  poc_cycle[i][j]//may be ue(v) or se(v)  if(bits_for_temporal_id_in_buffer_descriptions > 0 ) temporal_id_poc[i][j]//u(v) } if( number_of_negative_pictures + number_of_positive_pictures < max_num_ref_frames ) {  combine_with_reference_flag //u(1)  if(combine_with_reference_flag )   bd_combination_idx //u(v) }  } }

Examples of descriptions of the parameters in Listing (3) are given asfollows. A bd_poc_cycle_update_flag equal to 1 specifies that thepoc_cycle_pps[bd_idx][j] of the referenced buffer description should beoverridden for the current picture. In some configurations, futureframes may also override poc_cycle information. Ifbd_poc_cycle_update_flag is 0 then the original poc_cycle_pps[bd_idx][j]of the referenced buffer description are to be used.poc_cycle_pps_override[bd_idx][j] specifies the values to be used tooverride the values within the poc_cycle_pps[bd_idx][j] for the currentpicture only. In an alternative configuration,poc_cycle_pps_override[bd_idx][j] specifies an offset. For the currentpicture only,(poc_cycle_pps[bd_idx][j]+poc_cycle_pps_override[bd_idx][j]) may be usedinstead of poc_cycle_pps[bd_idx][j].

number_of_longterm_pictures[i] specifies the number of entries in thelist POCBD[i] and POC_CYCLE_BD[i]. The value ofnumber_of_longterm_pictures[i] shall be in the range of 0 tomax_num_ref_frames, inclusive. max_num_ref_frames specifies the maximumnumber of short term and long term reference frames. poc[i][j] specifiesPOC value and defines the value of the variable POCBD[i][j] asPOCBD[i][j]=poc[i][j]. poc[i][j] shall be in the range of 0 to MaxPOC-1.poc_cycle[i][j] (e.g., the cycle parameter) specifies poc_cycle valueand defines the value of the variable POC_CYCLE_BD asPC_CYCLE_BD[i][j]=poc_cycle[i][j]. poc_cycle[i][j] may be less than orequal to zero or may occupy a different numerical range.

temporal_id_poc[i][j] specifies a temporal identifier and shall berepresented by bits_(—) for_(—) temporal_(—) id_(—)in_buffer_descriptions bits. temporal_id_poc[i][j] defines the value ofthe variable TemporalIDBD[i][j] asTemporalIDBD[i][j]=temporal_id_poc[i][j]. temporal_id_poc[i][j] shall bein the range of 0 to max_temporal_layers_minus1, inclusive.max_temporal_layers_minus1+1 specifies the maximum number of temporallayers present in a sequence. In this approach, buffer description B maybe omitted from PPS.

In some configurations, number_of_longterm_pictures_pps[bd_idx] may betransmitted before the “for” loop illustrated in Listing (3), therebyavoiding a dependency on a slice header with PPS. Alternatively,bd_poc_cycle_update_flag may be replaced with another parameter,num_longterm_poccycle_override_count. For example, relevant code inListing (3) above may be replaced with “Ifnum_longterm_poccycle_override_count>0 then For (j=0;j<num_longterm_poccycle_override_count; j++) { . . . }.”

Some examples of ways in which the systems and methods described hereinmay be applied are given hereafter. Assume that a picture with POC=0 onis a long-term (reference) picture used by a picture with POC=MaxPOC−1and a picture with POC=0 from a subsequent picture set. The long-term(reference) picture may be indicated in different ways.

In a first way, there are two buffer descriptions in the PPS, includingbuffer description A: {POC=0,poc_cycle=0,temporalID} and bufferdescription B: {POC=0,poc_cycle=−1,temporalID}. The picture withPOC=MaxPOC−1 will point to buffer description A. The picture with POC=0from the subsequent picture set will refer to buffer description B.

In a second alternative way, the picture with POC=MaxPOC−1 will point tobuffer description A. The picture with POC=0 from the subsequent pictureset will refer to buffer description A and override thepoc_cycle_pps[B][0] value in the slice header to −1.

Some examples of configurations of the systems and methods disclosedherein are given hereafter. In one configuration, the 3-tuple (POC,poc_cycle, temporalID) may be replaced with the 2-tuple (LTSlotIdx,temporalID). LTSlotIndex may be a slot index that points to a locationin the long-term DPB. One possible benefit of this approach is to reducebitrate overhead.

In another configuration, the 3-tuple (POC, poc_cycle, temporalID) maybe replaced with (f(POC, poc_cycle), temporalID), where f(POC,poc_cycle) is a function (e.g., look-up table) that maps the two-tuple(POC, poc_cycle) to an index.

In some configurations, some or all information typically contained inthe PPS and/or in buffer descriptions may be additionally oralternatively carried in an Adaptive Slice Parameter Set or AdaptationParameter Set (APS). This information includes one or more of:number_of_longterm_pictures[i], poc[i][j], poc_cycle[i][j],temporal_id_poc[i][j], number_of_longterm_pictures_pps[i], poc_pps[i][j], poc_cycle_pps [i][j] and temporal_id_poc_pps [i][j]. Forexample, The Adaptive Slice Parameter Set or Adaptation Parameter Set(APS) may include one or more of a number of reference pictures (e.g.,number_of_longterm_pictures[i]), a picture order count (e.g.,poc[i][j]), a picture order count cycle parameter (e.g.,poc_cycle[i][j]), a temporal identifier picture order count parameter(e.g., temporal_id_poc[i][j]), a picture parameter set number ofreference pictures (e.g., number_of_longterm_pictures_pps[i]), a pictureparameter set picture order count (e.g., poc_pps[i][j]), a pictureparameter set picture order count cycle parameter (e.g.,poc_cycle_pps[i][j]) and a picture parameter set temporal identifierpicture order count parameter (e.g., temporal_id_poc_pps [i][j]).

In some configurations, the information poc_cycle[i][j] may only besignaled (e.g., from an encoder 108 to the decoder 102, 202) if it isdifferent than 0. In this case, an alternate syntax may be defined.

In an yet another configuration, some or all information typicallycontained in the PPS and/or in the buffer descriptions may additionallyor alternatively be carried in a slice header separately from the bufferdescription information. For example, the slice header may carry(separately from the buffer description container) one or more of anumber of reference pictures (e.g., number_of_longterm_pictures[i]), apicture order count (e.g., poc[i][j]), a picture order count cycleparameter (e.g., poc_cycle[i][j]), a temporal identifier picture ordercount parameter (e.g., temporal_id_poc[i][j]), a picture parameter setnumber of reference pictures (e.g., number_of_longterm_pictures_pps[i]),a picture parameter set picture order count (e.g., poc_pps[i][j]), apicture parameter set picture order count cycle parameter (e.g.,poc_cycle_pps[i][j]) and a picture parameter set temporal identifierpicture order count parameter (e.g., temporal_id_poc_pps[i][j]).

In an alternative configuration, a long term (reference) picture may besignaled by indexing it as x.y, where x=poc[i][j] or poc_pps[i][j] and yis a new information subindex that defines an additionalnamespace/numberspace for subindexing long term (reference) pictures. Inthis case, the x and y entries may be sent in PPS and/or bufferdescriptions (in a slice header) for each long term (reference) picture.

In some configurations, all (reference) pictures (e.g., long-term andshort-term) are referenced using either delta referencing (usingdeltaPOC and temporalID, for example) or absolute referencing (usingPOC, poc_cycle and temporalID, for example). For example, the entiredecoded picture buffer (DPB) may contain a set of received pictures. Asubset of these received pictures may use delta referencing and theremaining received pictures may use absolute referencing. It should benoted that prior approaches do not specify the same absolute referencingas given in accordance with the systems and methods disclosed herein(using POC and poc_cycle, for example). It should be noted that one ormore of the configurations of buffer descriptions and syntaxes describedmay be implemented in combination with one or more of the methods and/orapproaches described herein.

FIG. 3 is a flow diagram illustrating one configuration of a method 300for tracking a reference picture with reduced overhead referencing. Anelectronic device 204 (e.g., decoder 202) may receive 302 a bitstream.For example, the decoder 202 may receive 302 a bitstream 214 thatincludes an encoded reference picture (and other encoded pictures, forinstance). In some configurations, the bitstream 214 may also includeoverhead information (e.g., PPS, buffer description information,parameters, wrap indicators, reference picture designation oridentifier, etc.).

The electronic device 204 may decode 304 a portion of the bitstream 214to produce a decoded reference picture. For example, the decoder 202 maydecode 304 a portion of the bitstream 214 to produce a decoded referencepicture that is stored in frame memory 264. It should be noted that oneor more portions of the bitstream 214 may be decoded 304 to produce oneor more decoded reference pictures.

The electronic device 204 may track 306 the decoded reference picture ina decoded picture buffer (DPB) with reduced overhead referencing. Forexample, the electronic device 204 may associate a cycle parameter withthe decoded reference picture and modify (e.g., decrement or increment)the cycle parameter if a wrap indicator is received or if a transitionbetween picture sets is determined. Other approaches may be used fortracking 306 the decoded reference picture. Greater detail is givenbelow. It should be noted that the DPB may include one or more decodedreference pictures.

The electronic device 204 may decode 308 the picture based on one ormore decoded reference pictures. For example, a portion of the bitstream214 (other than the portion decoded 304 to produce the decoded referencepicture) may be decoded 308 based on the reference picture. Forinstance, the decoded reference picture (that has been tracked in theDPB) may be provided to a motion compensation module 260 in order togenerate an inter-frame prediction signal 268 based on an inter-frameprediction mechanism. The inter-frame prediction signal 268 may then beused to decode 310 the picture. In some configurations or instances, oneor more decoded reference pictures may be tracked 306 and used to decode308 the picture.

FIG. 4 is a flow diagram illustrating a more specific configuration of amethod 400 for tracking a reference picture with reduced overheadreferencing. This method 400 may be one approach for tracking whichpicture is being referenced when POCs are reused. An electronic device204 (e.g., decoder 202) may receive 402 a bitstream 214. For example,the decoder 202 may receive 402 a bitstream 214 that includes an encodedreference picture (and other encoded pictures, for instance). In someconfigurations, the bitstream 214 may include overhead information(e.g., PPS, buffer description information, parameters, wrap indicators,reference picture designation or identifier, etc.).

The electronic device 204 may decode 404 a portion of the bitstream 214to produce a decoded reference picture. For example, the decoder 202 maydecode 404 a portion of the bitstream 214 to produce a decoded referencepicture that is stored in frame memory 264. It should be noted that oneor more portions of the bitstream 214 may be decoded 404 to produce oneor more decoded reference pictures.

The electronic device 204 may associate 406 a cycle parameter with adecoded picture set that includes the decoded reference picture. Forexample, the electronic device 204 may associate 406 a cycle parameter“poc_cycle” with a decoded picture set that includes the decodedreference picture.

The cycle parameter “poc_cycle” may be defined as follows. When a fixednumber of bits are used to represent the POC of a picture in a range [0,. . . , MaxPOC−1], MaxPOC unique integer values exist. If the number ofpictures being encoded exceeds MaxPOC, a picture numbering mechanismmust reuse already assigned POC values. The POC numbering thenprogresses as follows in one example: . . . , [0, . . . ,MaxPOC−1]_(n−2), [0, . . . , MaxPOC−1]_(n−1), [0, . . . , MaxPOC-1]_(n),[0, . . . , MaxPOC−1]_(n+1), . . . . The subscript in this exampledenotes the number of times the set [0, . . . , MaxPOC-1] has beenrepeated. This subscript or the number of times the set [0, . . . ,MaxPOC−1] has been repeated may be denoted as MaxPOCSetIndex. Forexample, a picture with POC=0 and MaxPOCSetIndex=n represents the(n*MaxPOC+1)^(th) picture of the sequence (with an assumption thatpicture set numbering starts with 1, for instance). Additional detailregarding the cycle parameter “poc_cycle” is given in connection withFIG. 5 below.

The electronic device 204 may determine 408 whether a wrap indicator isreceived. For example, each time an encoder 108 or transmittingelectronic device A 104 a reaches a predetermined maximum number ofpictures in a set of pictures, the encoder 108 or transmittingelectronic device A 104 a may send a wrap indicator that is received bythe decoder 102 or receiving electronic device B 104 b to indicate thatanother set of pictures is being sent (e.g., a POC is resetting orstarting another cycle). Greater detail is given in connection with FIG.6 below.

If the electronic device 204 determines 408 that a wrap indicator wasreceived, the electronic device 204 may modify 410 (e.g., decrement) thecycle parameter. For example, the electronic device 204 decrements cycleparameters for each picture or each set of pictures in the DPB. Inanother example, the electronic device 204 may increment the cycleparameter.

The electronic device 204 may decode 412 a picture based on the decodedreference picture. For example, a portion of the bitstream 214 (otherthan the portion decoded 404 to produce the decoded reference picture)may be decoded 412 based on the reference picture. For instance, thedecoded reference picture (that has been tracked in the DPB) may beprovided to a motion compensation module 260 in order to generate aninter-frame prediction signal 268 based on an inter-frame predictionmechanism. The inter-frame prediction signal 268 may then be used todecode 412 the picture. In some configurations or instances, one or moredecoded reference pictures may be used to decode 412 the picture.

FIG. 5 is a diagram illustrating one example of multiple picture setsreferenced by cycle parameters. More specifically, FIG. 5 illustrates anexample of tracking a reference picture with reduced overheadreferencing using a cycle parameter. In particular, FIG. 5 illustrates acycle parameter (e.g., poc_cycle=−1) associated with picture set A 507a, a cycle parameter (e.g., poc_cycle=0) associated with picture set B507 b and a cycle parameter (e.g., poc_cycle=+1) associated with pictureset C 507 c. However, it should be noted that picture set A 507 a may ormay not be the first picture set in a sequence of frames. For example,one or more picture sets may precede picture set A 507 a. Furthermore,it should be noted that picture set C 507 c may or may not be the lastpicture set in a sequence of frames. For example, one or more picturesets may follow picture set C 507 c.

Each picture set 507 a-c may include one or more pictures 501 a-n, 503a-n, 505 a-n. In this example, each picture set 507 a-c includes MaxPOCpictures 501, 503, 505. In particular, each picture 501, 503, 505 mayhave a corresponding picture order count (POC), denoted as [0, 1, 2, . .. , MaxPOC−1] in FIG. 5.

In one example, the poc_cycle of the current decoded picture may be setto 0 for computing the poc_cycle of other pictures. In some cases,pictures may be decoded out of order. For example, a decoder may see 503b, then 505 a and then 503 c. In this example, assume that a picturebeing currently decoded is a picture 503 b in picture set B 507 b withPOC=1. The poc_cycle of another picture, such as a reference picture,may then be calculated based on the poc_cycle of the current decodedpicture.

FIG. 6 is a diagram illustrating one example of signaling a wrapindicator in accordance with the systems and methods disclosed herein.In this example, several pictures 601 a-n, 603 a are illustrated. Thefirst picture 601 a with POC=0 is a reference picture for the remainderof the pictures 601 b-n, 603 a illustrated in FIG. 6. In particular,FIG. 6 illustrates an association or correspondence 609 between thereference picture 601 a and the other pictures 601 b-n, 603 a. Forexample, the picture 601 a with POC=0 may be a long term referencepicture 601 a to be kept in the DPB for decoding other pictures 601 b-n,603 a.

As illustrated in FIG. 6, POC numbers 0 through MaxPOC−1 and a reused 0may respectively correspond to the pictures 601 a-n, 603 a. A first setof pictures 601-n may correspond to POC numbers 0 through MaxPOC−1. Asdescribed above, each set of pictures (with POC numbers 0 throughMaxPOC−1) may correspond to a cycle parameter (e.g., poc_cycle).

In one configuration, a wrap indicator may be signaled 611 at the firsttransition between one picture set and a subsequent later picture set.For example, the first time the POC numbering transitions from one [0, .. . , MaxPOC−1] set to the next, the wrap indicator may be signaled 611.In some configurations, the wrap indicator signaled may be a protectedmessage denoted “poc_wraparound.” As used herein, “signaled” may meancommunicated between an encoder and a decoder. In some configurations,“signaled” may also mean communicated between different electronicdevices.

A protected message may be a message that must be received by theelectronic device 204 in order to maintain a desired functionality suchas detection of lost pictures. One mechanism to transmit a message as aprotected message is to assign a higher priority to the protectedmessage when compared to other information messages. An intelligentdevice (e.g., a network congestion control agent) may then examine thispriority assignment and drop lower priority messages to meet constraintssuch as available network bandwidth.

In some configurations, the wrap indicator (e.g., poc_wraparound)message may be signaled in the Picture Parameter Set (PPS), SliceHeader, Adaptive Parameter Set (APS) or any suitable location in thebitstream. Additionally or alternatively, the wrap indicator may besignaled out-of-band (e.g., separate from the picture bitstream). Eachtime the wrap indicator (e.g., poc_wraparound message) is received bythe decoder 102, the cycle parameter (e.g., poc_cycle) for every picture(e.g., every picture set) in the DPB may be decremented (by 1, forexample).

FIG. 7 is a flow diagram illustrating another more specificconfiguration of a method 700 for tracking a reference picture withreduced overhead referencing. This method 700 may be another approachfor tracking which picture is being referenced when POCs are reused. Anelectronic device 204 (e.g., decoder 202) may receive 702 a bitstream.For example, the decoder 202 may receive 702 a bitstream 214 thatincludes an encoded reference picture. In some configurations, thebitstream 214 may also include overhead information (e.g., PPS, bufferdescription information, parameters, reference picture designation oridentifier, etc.).

The electronic device 204 may decode 704 a portion of the bitstream toproduce a decoded reference picture. For example, the decoder 202 maydecode 704 a portion of the bitstream 214 to produce a decoded referencepicture that is stored in frame memory 264. It should be noted that oneor more portions of the bitstream 214 may be decoded 404 to produce oneor more decoded reference pictures.

The electronic device 204 may associate 706 a cycle parameter with adecoded picture set that includes the decoded reference picture. Forexample, the electronic device 204 may associate 706 a cycle parameter“poc_cycle” with a decoded picture set or each picture in a decodedpicture set that includes the decoded reference picture. The cycleparameter “poc_cycle” is described in greater detail above.

The electronic device 204 may determine 708 whether a transition hasoccurred between picture sets. For example, the transition may bedetermined 708 by examining the POC of a current picture being decoded(e.g., CurPOC) and comparing it to the POC of the last picture that wasdecoded (e.g., LastPOC). For instance, if the POC of the current picture(e.g., CurPOC) being decoded is less than the POC of the last decodedpicture (e.g., LastPOC) and LastPOC−CurPOC is greater than a thresholdTH_FWD, then a transition from an earlier picture set to a later pictureset may be determined 708. However, if the POC of the current picturebeing decoded (e.g., CurPOC) is greater than the POC of the last picturethat was decoded (e.g., LastPOC) and CurPOC−LastPOC is greater than athreshold TH_BCKWD, then a transition from a later picture set to anearlier picture set may be determined 708. For all other cases, it maybe determined 708 that no transition has occurred. In someconfigurations, the thresholds may take on valuesTH_FWD=TH_BCKWD=MaxPOC/2.

If the electronic device 204 determines 708 that a transition hasoccurred between two picture sets, the electronic device 204 may modify710 the cycle parameter. For example, the electronic device 204 maydecrement cycle parameters for each picture or each set of pictures inthe DPB when the transition is from an earlier picture set. In anotherexample, the electronic device 204 may increment the cycle parametersfor each picture or each set of pictures in the DPB when the transitionis from a later picture set. Thus, an update of all reference picturecycle parameters may be carried out with respect to the picture beingdecoded. This update procedure (e.g., determining 708 whether atransition has occurred between picture sets and possibly modifying 710the cycle parameter(s)) may be executed once for each picture beingdecoded.

One alternative definition of the cycle parameter “poc_cycle” may bethat the poc_cycle for the picture (currently) being decoded is 0. Thus,the set of pictures that includes the picture currently being decodedmay be 0.

The poc_cycle of any other picture, such as the reference picture, maybe calculated as the MaxPOCSetIndex of the reference picture minus theMaxPOCSetIndex of the picture being decoded. For example, if theMaxPOCSetIndex of the picture being decoded is n and the referencepicture has a MaxPOCSetIndex that is n−1, then the poc_cycle of thereference picture may be (n−1)−n=−1.

It should be noted that the poc_cycle for a reference picture may dependon the MaxPOCSetIndex distance between the reference picture and thepicture being decoded. This can be determined implicitly by keepingtrack of transitions (e.g., determining 708 whether a transition hasoccurred) between one picture set of [0, . . . , MaxPOC−1] and the otherpicture set [0, . . . , MaxPOC−1] at both the encoder 108 and decoder102.

The electronic device 204 may decode 712 a picture based on the decodedreference picture. For example, a portion of the bitstream 214 (otherthan the portion decoded 704 to produce the decoded reference picture)may be decoded 712 based on the decoded reference picture. For example,the decoded reference picture (that has been tracked in the DPB) may beprovided to a motion compensation module 260 in order to generate aninter-frame prediction signal 268 based on an inter-frame predictionmechanism. The inter-frame prediction signal 268 may then be used todecode 712 the picture. In some configurations or instances, one or moredecoded reference pictures may be used to decode 712 the picture.

FIG. 8 is a flow diagram illustrating one configuration of a method 800for determining whether a transition has occurred between picture sets.For example, FIG. 8 provides one example of determining 708 whether atransition has occurred between picture sets as illustrated in FIG. 7.The electronic device 204 may determine 802 whether the POC of thecurrent picture being decoded (denoted “CurPOC,” for example) is lessthan the POC of the last decoded picture (denoted “LastPOC,” forexample). For instance, the electronic device 204 may compare a POC of acurrent picture being decoded (e.g., CurPOC) to a POC of a picture thatwas decoded last (e.g., LastPOC) to make this determination 802.

If CurPOC<LastPOC, the electronic device 204 may determine 808 whetherLastPOC−CurPOC is greater than a threshold TH_FWD. If LastPOC−CurPOC isgreater than a threshold TH_FWD, the electronic device 204 may determine808 that a transition from an earlier picture set to a later picture sethas occurred. However, if LastPOC−CurPOC is not greater than TH_FWD, theelectronic device 204 may determine 808 that no transition has occurred.

If CurPOC is not less than LastPOC, then the electronic device 204 maydetermine 804 whether CurPOC is greater than LastPOC. If the electronicdevice 204 determines 804 that CurPOC is greater than LastPOC, then theelectronic device 204 may determine 806 whether CurPOC−LastPOC isgreater than a threshold TH_BCKWD. If the electronic device determines806 that CurPOC−LastPOC is greater than a threshold TH_BCKWD, then theelectronic device 204 may determine 806 that a transition from a laterpicture set to an earlier picture set has occurred. If the electronicdevice determines 806 that CurPOC−LastPOC is not greater than athreshold TH_BCKWD, then the electronic device 204 may determine 806that no transition has occurred.

If the electronic device 204 determines 804 that CurPOC is not greaterthan LastPOC, the electronic device may determine 804 that no transitionhas occurred. In some configurations, the thresholds may take on valuesTH_FWD=TH_BCKWD=MaxPOC/2.

FIG. 9 is a flow diagram illustrating another more specificconfiguration of a method 900 for tracking a reference picture withreduced overhead referencing. This method 900 may be one approach fortracking which picture is being referenced when POCs are reused. Anelectronic device 204 (e.g., decoder 202) may receive 902 a bitstream214. For example, the decoder 202 may receive 902 a bitstream 214 thatincludes an encoded reference picture (and other encoded pictures, forinstance). In some configurations, the bitstream 214 may includeoverhead information (e.g., PPS, buffer description information,parameters, reference picture designation or identifier, etc.).

The electronic device 204 may decode 904 a portion of the bitstream 214to produce a decoded reference picture. For example, the decoder 202 maydecode 904 a portion of the bitstream 214 to produce a decoded referencepicture that is stored in frame memory 264. It should be noted that oneor more portions of the bitstream 214 may be decoded 904 to produce oneor more decoded reference pictures.

The electronic device 204 may associate 906 a cycle parameter with adecoded picture set that includes the decoded reference picture. Forexample, the electronic device 204 may associate 906 a cycle parameter“poc_cycle” with a decoded picture set that includes the decodedreference picture.

The electronic device 204 may determine 908 whether a transition hasoccurred between picture sets. For example, each time a decoder 102receives a predetermined maximum number of pictures in a set of pictures(and receives an additional picture), the decoder 102 or electronicdevice B 104 b may determine 908 that a transition has occurred betweentwo picture sets. In another example, each time a decoder 102 detects acycle in POC (e.g., restarting from a maximum value to a minimum value),the decoder 102 or electronic device B 104 b may determine 908 that atransition has occurred between two picture sets.

If the electronic device 204 determines 908 that a transition hasoccurred between picture sets, the electronic device 204 may modify 910(e.g., decrement) the cycle parameter. For example, the electronicdevice 204 decrements cycle parameters for each picture or each set ofpictures in the DPB. In another example, the electronic device 204 mayincrement the cycle parameter.

The electronic device 204 may decode 912 a picture based on the decodedreference picture. For example, a portion of the bitstream 214 (otherthan the portion decoded 904 to produce the decoded reference picture)may be decoded 912 based on the reference picture. For instance, thedecoded reference picture (that has been tracked in the DPB) may beprovided to a motion compensation module 260 in order to generate aninter-frame prediction signal 268 based on an inter-frame predictionmechanism. The inter-frame prediction signal 268 may then be used todecode 912 the picture. In some configurations or instances, one or moredecoded reference pictures may be used to decode 912 the picture.

FIG. 10 illustrates various components that may be utilized in anelectronic device 1004. The electronic device 1004 may be implemented asone or more of the electronic devices (e.g., electronic devices 104,204) described previously.

The electronic device 1004 includes a processor 1017 that controlsoperation of the electronic device 1004. The processor 1017 may also bereferred to as a CPU. Memory 1011, which may include both read-onlymemory (ROM), random access memory (RAM) or any type of device that maystore information, provides instructions 1013 a (e.g., executableinstructions) and data 1015 a to the processor 1017. A portion of thememory 1011 may also include non-volatile random access memory (NVRAM).The memory 1011 may be in electronic communication with the processor1017.

Instructions 1013 b and data 1015 b may also reside in the processor1017. Instructions 1013 b and/or data 1015 b loaded into the processor1017 may also include instructions 1013 a and/or data 1015 a from memory1011 that were loaded for execution or processing by the processor 1017.The instructions 1013 b may be executed by the processor 1017 toimplement the systems and methods disclosed herein.

The electronic device 1004 may include one or more communicationinterfaces 1019 for communicating with other electronic devices. Thecommunication interfaces 1019 may be based on wired communicationtechnology, wireless communication technology, or both. Examples ofcommunication interfaces 1019 include a serial port, a parallel port, aUniversal Serial Bus (USB), an Ethernet adapter, an IEEE 1394 businterface, a small computer system interface (SCSI) bus interface, aninfrared (IR) communication port, a Bluetooth wireless communicationadapter, a wireless transceiver in accordance with 3^(rd) GenerationPartnership Project (3GPP) specifications and so forth.

The electronic device 1004 may include one or more output devices 1023and one or more input devices 1021. Examples of output devices 1023include a speaker, printer, etc. One type of output device that may beincluded in an electronic device 1004 is a display device 1025. Displaydevices 1025 used with configurations disclosed herein may utilize anysuitable image projection technology, such as a cathode ray tube (CRT),liquid crystal display (LCD), light-emitting diode (LED), gas plasma,electroluminescence or the like. A display controller 1027 may beprovided for converting data stored in the memory 1011 into text,graphics, and/or moving images (as appropriate) shown on the display1025. Examples of input devices 1021 include a keyboard, mouse,microphone, remote control device, button, joystick, trackball,touchpad, touchscreen, lightpen, etc.

The various components of the electronic device 1004 are coupledtogether by a bus system 1029, which may include a power bus, a controlsignal bus and a status signal bus, in addition to a data bus. However,for the sake of clarity, the various buses are illustrated in FIG. 10 asthe bus system 1029. The electronic device 1004 illustrated in FIG. 10is a functional block diagram rather than a listing of specificcomponents.

The term “computer-readable medium” refers to any available medium thatcan be accessed by a computer or a processor. The term“computer-readable medium,” as used herein, may denote a computer-and/or processor-readable medium that is non-transitory and tangible. Byway of example, and not limitation, a computer-readable orprocessor-readable medium may comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer or processor. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray® disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.

It should be noted that one or more of the methods described herein maybe implemented in and/or performed using hardware. For example, one ormore of the methods or approaches described herein may be implemented inand/or realized using a chipset, an application-specific integratedcircuit (ASIC), a large-scale integrated circuit (LSI) or integratedcircuit, etc.

Each of the methods disclosed herein comprises one or more steps oractions for achieving the described method. The method steps and/oractions may be interchanged with one another and/or combined into asingle step without departing from the scope of the claims. In otherwords, unless a specific order of steps or actions is required forproper operation of the method that is being described, the order and/oruse of specific steps and/or actions may be modified without departingfrom the scope of the claims.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the systems, methods, and apparatus described herein withoutdeparting from the scope of the claims.

What is claimed is:
 1. A method for decoding a video bitstreamcomprising: receiving a respective buffer description for each of one ormore decoded reference pictures from the video bitstream; wherein therespective buffer descriptions include a poc cycle parameter for one ormore long term reference pictures in the one or more decoded referencepictures, and wherein the poc cycle parameter is used to calculate apicture order count (POC) for the decoded long term reference pictures;identifying one or more decoded reference pictures for a current picturefrom a decoded picture buffer, based on the POC for the decoded longterm reference pictures; decoding the current picture using inter-frameprediction based on the identified one or more decoded referencepictures; and buffering the decoded picture in the decoded picturebuffer.
 2. The method of claim 1, wherein the poc cycle parameter is anindicator to start another poc cycle.
 3. The method of claim 1, whereinthe poc cycle parameter is in a slice header.
 4. An electronic deviceconfigured for decoding a video bitstream, comprising: a processorconfigured to: receive a respective buffer description for each of oneor more decoded reference pictures from the video bitstream; wherein thebuffer descriptions include a poc cycle parameter for one or more longterm reference pictures in the one or more decoded reference pictures,and the poc cycle parameter is used to calculate a picture order count(POC) for the decoded long term reference pictures; identify one or moredecoded reference pictures for a current picture from a decoded picturebuffer, based on the POC for the decoded long term reference pictures;decode the current picture using inter-frame prediction based on theidentified one or more decoded reference pictures; and buffer saiddecoded picture in the decoded picture buffer.
 5. The method of claim 1,wherein the poc cycle parameter indicates a decoded picture set to whichthe one or more long term reference pictures belong.
 6. The device ofclaim 4, wherein the poc cycle parameter indicates a decoded picture setto which the one or more long term reference pictures belong.